North end of US highway 1: Fort Kent, Maine

US 1 has been around since the beginning in 1926, and its north
end has always been in Fort Kent ME. The photo below shows one of the
last northbound reassurance markers...

Taylor, Oct. 2004

...although you're essentially heading south at that point (more
on that below). US 1 is co-signed ahead with ME hwy. 161, through the
intersection with ME 11, to the bridge that crosses the St. John
River to Clair, New Brunswick. Below we're looking southwest on Main
Street, approaching the north end of US 1:

Clements, May 2001

The building in the foreground is the Masonic Lodge, and behind
that is US Customs. Between the two, you can turn right and cross the
bridge visible at far right. Halfway across that span is the
international boundary with Canada. The signs at far right are shown
more closely below:

Taylor, Oct. 2004

ME 161 ahead is about 30 miles long, and goes a bit beyond
Allagash before dead-ending. Note how the historic marker implies
that US 1 "begins" in Key West. On the other side of this sign, the
story is slightly different:

Clements, May 2001

According to this side, Key West marks the "end" of the route. I
bring this up because Becky reports that some Ft. Kent residents
believe they are living "on the top of the world", and they can be
quite insistent that US 1 begins there, and ends in
Florida. While you're checking out that sign, you can see further evidence of this by taking a few steps closer to the river and checking out the new civic monument dedicated to US 1:

Listemaa, July 2011

If you're curious about the text on those side panels, Greg Corkum has sent detailed photos, which you can view here (and on adjacent shots in the photostream). It's a cool monument, with steps leading up to a nice view of the bridge at far left. It's not often that you come across a place that has celebrated a highway terminus to this extent. But US 1 doesn't actually have an official "beginning" or
"ending"; it simply has a north and a south terminus. However, Becky
reports that this concept was not acknowlegded, so I imagine neither
would it be well-received to point out the fact that five states (six
including Alaska) extend further north than Maine...

...nor the fact that Ft. Kent isn't even the northernmost point in
Maine. For that reason, I personally don't think US 1 should be
signed all the way to Ft. Kent. If it were up to me, I'd end the
designation at the Madawaska ME border crossing, which connects with
the city of Edmundston NB and a more heavily-used Canadian highway.
From Madawaska, US 1 actually goes south and west to reach Ft.
Kent. So rather than signing that segment as "northbound US 1", I
think it would make more sense to designate it as southbound ME
11.

But I digress. Let's go back to US 1 and continue "north" (which is actually southwest); here's a photo from a bit further ahead (closer to
the bridge):

Taylor, Oct. 2004

This intersection marks the official north end of US 1: straight
ahead is ME 161, and right is the bridge to Clair (the green street
sign says "Border Crsg"). If you take that right turn, this next shot
shows the view looking northwest over the bridge to Canada:

Clements, May 2001

The international boundary here is formed by the St. John River; the town of
Clair is on the far side. US 1 is actually signed in New Brunswick:

Poitras, July 2010

That's looking southwest on Rue Principale in Clair (the French equivalent of "Main Street", I believe), approaching the left turn that leads to the bridge over to Ft. Kent (Canadian customs is behind the camera). Coming over that bridge, you first stop here...

Mortell,
1995

...and then you're greeted with this sign:

Taylor, Oct. 2004

That sign actually means "TO hwy. 11". About a block in that direction is the wooden signboard mentioned above. In addition to that, there are a couple other US 1 points of interest in town. One of them is just to the north of the wooden sign, right up against the river levee - it's a sort of monument (view photo). Also, if you go to the right for about a block, there's another wooden sign at the municipal center (photo).

Anyway, the beginning of US 1 is to the left - if you make that turn, you'll
soon see the first "southbound" reassurance marker on US 1...

Taylor, Oct. 2004

...though, as I've pointed out, that bend to the left swings you almost due
north. This assembly is at the junction with ME 11, the north beginning of which
is currently to the right. I'd extend it ahead, replacing US 1 until it reaches
the bridge at Madawaska.